1. Field of the Invention
The present invention relates to a machine learning apparatus, a motor control apparatus, a processing machine, and a machine learning method. In particular, the present invention relates to a machine learning apparatus for optimizing a cycle processing time of a processing machine, a motor control apparatus provided with the machine learning apparatus, a processing machine, and a machine learning method.
2. Description of the Related Art
Upon a motor is operated, temperature of a winding of the motor increases. Further, when a certain period of time elapses since the motor starts operating, the temperature of the winding is saturated so that the winding is maintained at a high temperature (This temperature is referred to as “saturation temperature” hereinafter). In the winding having such a saturation temperature, when application of electric current to the winding is continued while the temperature of the winding exceeds its upper limit, the winding of the motor can burn out. Alternatively, even when the temperature of the winding is not saturated, if the temperature of the winding exceeds its upper limit, the winding of the motor can be damaged.
Thus, in drive control of a motor, the temperature of a winding has conventionally been monitored, and, when the temperature of the winding exceeds a predetermined temperature threshold, application of electric current to the winding is discontinued to prevent the winding from burning out or being damaged (see, for example, Japanese Patent Application Laid-open No. 2013-70485). The above temperature threshold is referred to as “overheat alarm level”.
Furthermore, in a processing machine, a motor is employed for a main spindle for rotating a tool, and accordingly, the temperature of the motor for the main spindle is controlled to be less than the overheat alarm level, to prevent a failure of the motor.
Specifically, in a processing machine, when a processing operation having a predetermined processing pattern is constantly repeated, the temperature of a winding of the motor exceeds its upper limit, and accordingly, processing downtime is set after one cycle of processing operation time. In other words, in the processing downtime, a motor control apparatus tries not to apply electric current to the winding of the motor. In this specification, the sum of the processing operation time and the processing downtime is referred to as “one-cycle processing time”.
However, when the processing downtime is set in the motor control apparatus as described above, it is necessary that an operator should actually operate the processing machine, to find, through trial and error, the shortest processing downtime which satisfies the fact that the temperature of the winding of the motor does not exceed an alarm level. Further, inaccurate setting of the processing downtime causes a burn out of the winding or a reduction in the operation rate of the processing machine. Thus, the operator requires a lot of labor and time to accurately find the processing downtime.